#反向传播算法，乘法节点
class mullayer:
    def __init__(self):
        self.x=None
        self.y=None


    def forward(self,x,y):
        self.x=x
        self.y=y
        out=x*y

        return out

    def backward(self,dout):
        dx =dout*self.y #调转x和y
        dy =dout*self.x

        return dx,dy
